This application claims priority to an application entitled xe2x80x9cState Synchronization Between Base Station and Mobile Station In CDMA Mobile Communication Systemxe2x80x9d filed in the Korean Industrial Property Office on Jun. 13, 1998 and assigned Serial No. 98-22217, the contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a mobile communication system and in particular, to a state synchronization method between a base station and a mobile station with a reduced signaling overhead during a packet data service in a MAC (Medium Access Control) sublayer of a CDMA (Code Division Multiple Access) mobile communication system.
2. Description of the Related Art
Mobile communication systems provide a circuit switch service and a packet data service. In the packet data service, signaling messages are frequently generated and compared with the circuit switch service. Packet data has a burst property, i.e. it is generated discontinuously. Therefore, a dedicated traffic channel and a dedicated control channel are discontinuously assigned to all users during a service time period in consideration of the following factors: a radio resource capacity, of the mobile communication system capability of a base station, in serving all users; and power consumption of a mobile station.
Instead, the dedicated channels are assigned during the occurrence of traffic. If a prescribed time period elapses after transmission of packet data, the dedicated channels are terminated, so that other users can use these resources. That is, channels are dynamically assigned. In a system providing the packet data service, the base station and mobile station undergo changes in states depending on whether data is generated, and therefore, an occurrence of a signaling messages between the base station and the mobile station is quite common. Hence, it is important to maintain synchronization between the base station and mobile station.
In a conventional CDMA mobile communication system, the circuit switch service has mainly been provided to synchronize the base station with the mobile station. Most of the signaling messages used in the conventional system are for processing call setup, handoff and call termination, and they are generated from a layer three. Upon transmission of a signaling message from the base station to the mobile station, a command is transmitted over a forward link, and the mobile station receiving the command transmits a response to the base station. The base station again transmits a confirm message to inform the mobile station that the command has been normally processed. Meanwhile, upon transmission of a signaling message from the mobile station to the base station, a request is transmitted over a reverse link, and the base station receiving the request transmits a response to the mobile station.
The back and forth transmission of signaling messages between the base station and the mobile station is defined as the signaling overhead of the communication system.
FIGS. 1A and 1B respectively illustrate conventional signaling message transmission processes when a base station (BS) informs a mobile station (MS) of an occurrence of an event and when the mobile station (MS) informs the base station (BS) of an occurrence of an event. These signaling message transmission processes are used for processing layer-3 signaling messages generated during call setup, handoff and call termination. However, since the above processes transmit and receive the signaling messages one by one, many radio resources are used and signaling overhead is increased, and hence it takes quite some time to maintain synchronization between the base station and the mobile station. Accordingly, system performance and efficiency are decreased.
It is an object of the present invention to provide a method for minimizing signaling overhead to maintain synchronization between a base station and a mobile station in a MAC sublayer of a mobile communication system having a packet data service which undergoes frequent state changes.
It is another object of the present invention to provide a method for reducing unnecessary consumption of radio resources and a synchronization time by variably performing a synchronization between a base station and a mobile station according to service circumstances or predetermined system conditions.
To achieve the above objects, the present invention provides a state synchronization method for transmitting packet data between a base station and a mobile station in a CDMA mobile communication system. The method includes the steps of: transmitting, at the base station, a state check message to the mobile station in an active state; receiving, at the base station, a response message from the mobile station; and analyzing the received response message to determine a state of the mobile station, terminating a corresponding channel, and transitioning the base station to the state of the mobile station.
According to the present invention, if the mobile station is in an active state the base station maintains the active state; if the mobile station is in a control hold state, the base station terminates a dedicated traffic channel to transition to the control hold state; if the mobile station is in a suspended state, the base station terminates the dedicated traffic channel to transition to the control hold state and then terminates a dedicated control channel to transition to the suspended state, and if the mobile station is not in one of the active state, control hold state, and the suspended state, the base station terminates the dedicated traffic channel to transition to the control hold state and terminates the dedicated control channel to transition to the suspended state, and terminates a common control channel to transition to a dormant state.
The present invention further provides a state synchronization method for transmitting packet data between a base station and a mobile station in a CDMA mobile communication system. The method includes the steps of transmitting, at the mobile station, a state check message to the base station in an active state; receiving, at the mobile station, a response message from the base station; and analyzing the received response message to determine a state of the base station, terminating a corresponding channel, and transitioning the mobile station to the state of the base station.
If the base station is in an active state, the mobile station maintains the active state; if the base station is in a control hold state, the mobile station terminates a dedicated traffic channel to transition to the control hold state; if the base station is in a suspended state, the mobile station terminates the dedicated traffic channel to transition to the control hold state and then terminates a dedicated control channel to transition to the suspended state; and if the base station is not in one of the active state, control hold state, and suspended state, the mobile station terminates the dedicated traffic channel to transition to the control hold state and terminates the dedicated control channel to transition to the suspended state, and terminates a common control channel to transition to a dormant state.